The present invention relates to a suspension for supporting a head of a disc drive stored in an information processing apparatus such as a personal computer, portable computer, etc.
FIG. 11 shows a part of a hard disc drive (HDD) 1. A carriage 2 of the disc drive 1 is turned around a shaft 2a by means of a motor 3 for positioning, such as a voice coil motor. The carriage 2 is composed of a coil portion 5 located near a magnet 4 of the motor 3, arms (also referred to as actuator arms) 6 fixed to the coil portion 5, suspensions 7 situated on the distal end side of the arms 6, heads 8 attached individually to the respective distal end portions of the suspensions 7, etc. Each head 8 can be moved to a desired track (recording surface) of a hard disc 9 by driving the carriage 2 by means of the motor 3.
Each head 8 includes a slider 10, which is situated in a position such that it can face the tracks of the disc 9, a transducer (not shown) which is provided on the slider 10, etc. When the slider 10 barely floats above the surface of the disc 9 as the disc 9 rotates at high speed, an air bearing is formed between the disc 9 and the slider 10.
FIGS. 12, 13 and 14 show an example of the conventional suspension 7. The suspension 7 comprises a load beam 11 formed of a thin precision plate spring, a flexure 12 formed of a very thin plate spring fixed to the distal end portion of the load beam 11, a base plate 13 fixed to the proximal portion of the beam 11. The slider 10 is mounted on a tongue 12a that is formed on the flexure 12. The stiffness of the flexure 12 is made so low that the attitude of the slider 10 floating low above the disc 9 can be flexibly changed.
A hemispherical support projection 15 protrudes from the distal end portion of the load beam 11 toward the flexure 12. As shown in FIG. 13, the distal end of the support projection 15 is in contact with the tongue 12a of the flexure 12. Therefore, the head 8 can make three-dimensional displacements, including pitching, rolling, etc., around the support projection 15. The projection 15, which is depressed inside, is also called a dimple in the art. The projection 15 may be provided on the flexure 12 instead of being formed on the load beam 11.
With the progress of miniaturization of modern information processing apparatuses such as personal computers, the shock resistance properties of hard disc drives (HDDs) have become an important factor. In the case of an information processing apparatus that uses a small-sized hard disc (2.5-inch HDD), such as a so-called notebook computer, the shock-absorbing capability of its casing is not good enough. In the case of a desktop computer (using a 3.5-inch HDD), on the other hand, the HDD may possibly be subjected to a relatively heavy shock if it is handled wrongly in assembling operation.
When the aforementioned conventional suspension 7 was subjected to a shock exceeding its tolerance limit, the head 8 behaved unsteadily, and the head 8 and the disc 9 were damaged. The inventors hereof observed the behavior of the shocked head 8 by using a high-speed camera and the like, and found that the head 8 and the disc 9 were damaged in the following manner. When the suspension 7 was shocked, the distal end portion of the load beam 11 sprang up, as shown in FIG. 14. Thereupon, the head 8 underwent pitching or rolling so that its corner portions (including a corner portion 8a) ran against the surface of the disc 9. A phenomenon called dimple separation such that the flexure 12 and the support projection 15 separate from each other, in particular, promotes the aforesaid problem.
FIG. 15 shows the result of measurement of the respective displacements of the head and the support projection obtained when the conventional suspension was shocked. Test conditions include the shock duration time of 1 msec and acceleration of 460 G. As shown in FIG. 15, the mean value for dimple separation for the time interval from 0 to 5.5 msec is as large as 0.21 mm. FIG. 16 shows the result of measurement of the change of the angle of inclination of the head in the pitching direction obtained when the conventional suspension was shocked. According to this test result, the range of inclination angle change of the head is as wide as 36.78.degree., and the head inclination reciprocates with relatively wide amplitudes in both the positive (+) and negative (-) directions.
Possibly, the occurrence of dimple separation and head inclination may be restrained by enhancing the stiffness of the flexure. If the stiffness of the flexure is increased, however, it is difficult to change the attitude of the slider flexibly when the slider floats low above the disc. Thus, stiffness of the flexure cannot be enhanced without a problem.